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PENSION AND OTHER POSTRETIREMENT BENEFIT PLANS (Nonunion) (Details) - USD ($) $ in Thousands | 3 Months Ended
--- | ---
Jun. 30, 2019 | Mar. 31, 2019 | Mar. 31, 2018
Pension and other postretirement benefit plans |  |  |
Pension settlement expense, pre-tax |  | $ 1,356 | $ 654
Pension settlement expense, net of tax |  | 1,007 | 486
Nonunion Defined Benefit Pension Plan |  |  |
Pension and other postretirement benefit plans |  |  |
Pension settlement expense, pre-tax |  | 1,356 | 654
Pension settlement expense, net of tax |  | 1,000 | 500
Lump-sum distributions |  | $ 14,900 | $ 4,800
Expected return on plan assets (as a percent) |  | 1.40% |
Nonunion Defined Benefit Pension Plan | Forecast |  |  |
Pension and other postretirement benefit plans |  |  |
Pension settlement expense, pre-tax | $ 2,000 |  |
Pension settlement expense, after-tax | 1,500 |  |
Employer contributions | $ 6,000 |  |
Expected return on plan assets (as a percent) | 0.00% |  |

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